For enhancing the performance of a computer system, the user may change the BIOS (basic input output system) settings of the computer system. For example, through the BIOS settings, the operating voltage or the operating frequency to be used in a control chip or a central processing unit on a motherboard is adjustable. For example, overclocking is the process of forcing a computer component to run at a higher clock rate than it was designed or designated by the manufacturer; and a dynamic voltage scaling process to increase voltage is known as overvolting.
Take the overvolting process for example. There are several optional operating voltages (e.g. 1.50V, 1.55V, 1.60V, 1.65V, 1.70V) shown on the BIOS setup menu. Via the BIOS setup menu, the user may select an operating voltage of a specified component in order to operate such a specified component at its optimal performance.
FIG. 1 is a schematic functional block diagram illustrating an overvolting control device of a memory of a motherboard according to the prior art. As shown in FIG. 1, a central processing unit (CPU) 12, a north bridge chip 14, a south bridge chip 16, a memory 18, a voltage regulator 20 and a reference voltage control circuit 22 are mounted on the motherboard 10. Generally, the operating voltage Vmem of the memory 18 is generated by the voltage regulator 20 according to a reference voltage Vref. By outputting different voltage values of the reference voltage Vref from the reference voltage control circuit 22, the operating voltage Vmem of the memory 18 is adjustable.
Please refer to FIG. 1 again. The reference voltage control circuit 22 is electrically connected to two general purpose I/O ports (I/O-1 and I/O-2 ports). Via the BIOS setup menu, the voltage levels at the I/O-1 and I/O-2 ports are selected and thus a desired reference voltage Vref is obtained. For example, if the I/O-1 and I/O-2 ports can be in a ground status or a floating status, four different voltage levels of the reference voltage Vref can be obtained. Hereinafter, the possible situations of obtaining four different voltage levels of the reference voltage Vref will be illustrated as follows.
In a case that the I/O-1 and I/O-2 ports are both in the floating statuses, the reference voltage Vref is 1.5V (assuming that Vcc is 3V). That is,
  Vref  =                              R          ⁢                                          ⁢          1                          2          ⁢          R          ⁢                                          ⁢          1                    ×      Vcc        =          1.5      ⁢                          ⁢      V      
In a case that the I/O-1 port is in the ground status but the I/O-2 port is in the floating status, the reference voltage Vref is obtained by the equation:
  Vref  =                    (                              R            ⁢                                                  ⁢            1                    //                      R            ⁢                                                  ⁢            2                          )                              R          ⁢                                          ⁢          1                +                  (                                    R              ⁢                                                          ⁢              1                        //                          R              ⁢                                                          ⁢              2                                )                      ×    Vcc  
In a case that the I/O-1 port is in the floating status but the I/O-2 port is in the ground status, the reference voltage Vref is obtained by the equation:
      V    ⁢                  ⁢    ref    =                    (                              R            ⁢                                                  ⁢            1                    //                      R            ⁢                                                  ⁢            3                          )                              R          ⁢                                          ⁢          1                +                  (                                    R              ⁢                                                          ⁢              1                        //                          R              ⁢                                                          ⁢              3                                )                      ×    Vcc  
In a case that the I/O-1 and I/O-2 ports are both in the ground statuses, the reference voltage Vref is 1.5V is obtained by the equation:
            V      ⁢                          ⁢      ref        =                            (                                                    R                ⁢                                                                  ⁢                1                            //                              R                ⁢                                                                  ⁢                2                                      //                          R              ⁢                                                          ⁢              3                                )                                      R            ⁢                                                  ⁢            1                    +                      (                                                            R                  ⁢                                                                          ⁢                  1                                //                                  R                  ⁢                                                                          ⁢                  2                                            //                              R                ⁢                                                                  ⁢                3                                      )                              ×      Vcc        ⁢        
In other words, if the numbers of the general purpose I/O ports and corresponding resistors of the reference voltage control circuit 22 are increased, more diverse voltage levels of the reference voltage Vref are obtainable. For example, if three general purpose I/O ports are used, eight voltage levels of the reference voltage Vref are obtainable.
Generally, the components of the motherboard whose operating voltages can be adjusted via the BIOS setup menus include for example the central processing unit, the north bridge chip, the south bridge chip and the memory. Assuming that these four components can provide eight kinds of operating voltages, a total of twelve general purpose I/O ports are required (i.e. 3×4=12). For a purpose of providing more kinds of operating voltages through the BIOS settings, more I/O ports are required.
As for the overclocking process, a clock generator is mounted on the motherboard. The clock generator may provide various clock signals of different operating frequencies. The clock signals are transmitted to the central processing unit, the north bridge chip, the south bridge chip and the memory in order to coordinate the actions of these components. Similarly, through the general purpose I/O ports, the operating frequencies of the clock signals can be fine-tuned.
Moreover, the overvolting process and the overclocking process implemented via the BIOS setup menu are very troublesome and time-consuming. After the operating voltages and operating frequencies of all components are set via BIOS setup menu, the set values should be stored in the BIOS. Until the computer system is re-started, the set values are loaded into the BIOS to implement the overvolting and overclocking processes.
Nowadays, some motherboard manufacturers provide application programs to implement the overvolting process or the overclocking process. Since these application programs need to be executed under specified operation systems and the computer system needs to be re-started after the set values are determined, this approach is also inconvenient.